From: Eric Biggers ebiggers@google.com

When asked to encrypt or decrypt 0 bytes, both the generic and x86 implementations of Salsa20 crash in blkcipher_walk_done(), either when doing 'kfree(walk->buffer)' or 'free_page((unsigned long)walk->page)', because walk->buffer and walk->page have not been initialized.

The bug is that Salsa20 is calling blkcipher_walk_done() even when nothing is in 'walk.nbytes'. But blkcipher_walk_done() is only meant to be called when a nonzero number of bytes have been provided.

The broken code is part of an optimization that tries to make only one call to salsa20_encrypt_bytes() to process inputs that are not evenly divisible by 64 bytes. To fix the bug, just remove this "optimization" and use the blkcipher_walk API the same way all the other users do.

Reproducer:

#include <linux/if_alg.h> #include <sys/socket.h> #include <unistd.h>

int main() { int algfd, reqfd; struct sockaddr_alg addr = { .salg_type = "skcipher", .salg_name = "salsa20", }; char key[16] = { 0 };

algfd = socket(AF_ALG, SOCK_SEQPACKET, 0); bind(algfd, (void *)&addr, sizeof(addr)); reqfd = accept(algfd, 0, 0); setsockopt(algfd, SOL_ALG, ALG_SET_KEY, key, sizeof(key)); read(reqfd, key, sizeof(key)); }

Reported-by: syzbot syzkaller@googlegroups.com Fixes: eb6f13eb9f81 ("[CRYPTO] salsa20_generic: Fix multi-page processing") Cc: stable@vger.kernel.org # v2.6.25+ Signed-off-by: Eric Biggers ebiggers@google.com --- arch/x86/crypto/salsa20_glue.c | 7 ------- crypto/salsa20_generic.c | 7 ------- 2 files changed, 14 deletions(-)

diff --git a/arch/x86/crypto/salsa20_glue.c b/arch/x86/crypto/salsa20_glue.c index 399a29d067d6..cb91a64a99e7 100644 --- a/arch/x86/crypto/salsa20_glue.c +++ b/arch/x86/crypto/salsa20_glue.c @@ -59,13 +59,6 @@ static int encrypt(struct blkcipher_desc *desc,

salsa20_ivsetup(ctx, walk.iv);

- if (likely(walk.nbytes == nbytes)) - { - salsa20_encrypt_bytes(ctx, walk.src.virt.addr, - walk.dst.virt.addr, nbytes); - return blkcipher_walk_done(desc, &walk, 0); - } - while (walk.nbytes >= 64) { salsa20_encrypt_bytes(ctx, walk.src.virt.addr, walk.dst.virt.addr, diff --git a/crypto/salsa20_generic.c b/crypto/salsa20_generic.c index f550b5d94630..d7da0eea5622 100644 --- a/crypto/salsa20_generic.c +++ b/crypto/salsa20_generic.c @@ -188,13 +188,6 @@ static int encrypt(struct blkcipher_desc *desc,

salsa20_ivsetup(ctx, walk.iv);

- if (likely(walk.nbytes == nbytes)) - { - salsa20_encrypt_bytes(ctx, walk.dst.virt.addr, - walk.src.virt.addr, nbytes); - return blkcipher_walk_done(desc, &walk, 0); - } - while (walk.nbytes >= 64) { salsa20_encrypt_bytes(ctx, walk.dst.virt.addr, walk.src.virt.addr,